Tile Drains Vs. Mole Drains

Subsurface Drainage

• Wet soil is detrimental to agricultural productivity. Subsurface drainage systems amend wet conditions for situations where surface drainage is inadequate, such as flat soils and areas with a high water table. Extensive tile -- pipe -- drain systems cover agricultural lands in North America. Mole drains are more modestly-scaled subsurface drainage systems; they drain water that enters the soil from above, not groundwater. Mole drains are made from shaping the soil with pipes and gravel used occasionally.

Tile Drains

• Tile drainage systems are composed of a perforated pipe laid in a shallow trench lined with gravel and geotextile fabric. They capture the water in the soil and groundwater for infiltration Their installation spans such large areas that tile drains have an altering effect on the drainage patterns of agricultural lands. Though they require maintenance tile drains are long-term drainage systems that form a major part of agricultural infrastructure, by turning marginal soils into productive ones.

Mole Drains

• Mole drains are unlined channels formed in clay subsoil by pulling equipment -- the mole -- through the soil. The soil needs to be at least 35 percent clay, in order to hold the shape of the channel after the mole has passed through. Mole drains last longer in short lengths because the water is discharged more quickly. They're are often used for short term purposes, such as seasonal flooding or to reclaim saline soils, and where cost is a constraint.

Life Span of Tile Drains and Mole Drains

• Tile drains become less effective if the perforated pipes or outlets become clogged. They're often replaced in that case. Ongoing maintenance is required to keep tile drains operating, they may be decommissioned when the land use changes from agricultural. Mole drainage channels can last for a few years or a few days. Water backing up in the channel instead of discharging can cause the channel to collapse; this outcome is taken into account but the time frame is not necessarily predictable.